A method of separating particulate material of differing size or density including the steps of: tumbling the particulate material to produce continuous or discrete avalanches (19) in the surface of the particulate material to move particles of smaller size (14) or higher density (22) towards the centre of the particulate material and particles of larger size (16) or lower density (24) radially outward from the centre of the particulate material; and extracting particles at selected radial locations (8, 10). A device for separating particulate material of differing size or density is also provided.